It is known to provide training, conditioning and exercising apparatus, frequently known as machines in which one or more elements, generally in the form of arms, can be moved by selected portions of the body against resistances or restraining forces or even against counteracting forces or movement so as to bring about a form of muscular development, muscular conditioning, muscular and vascular toning and, in general, improved coordination and physiological functioning.
While a wide variety of training means has been provided for this purpose, the means of particular interest here are those which comprise a transmission of the type having a pair of shafts and generally a certain transmission ratio between the speeds of rotation of these shafts, one of the shafts being connected to one of the aforementioned arms while the other shaft is connected to a retarder or resistance unit.
In general, an adequate training action can only be obtained if the transmission allows the arm to swing through at least at 180.degree..
In German Pat. No. 22 13 440, for example, the first shaft is provided with an arm which can be manipulated or otherwise displaced by a portion of the body of the user while the other shaft of the transmission is provided with an arm adapted to carry replaceable weights and, if desired, to be connected to a hydraulic or pneumatic loading unit.
One of the problems of a system in which the countervailing load is a weight on a swingable arm, is that the restraining force does not remain constant over the full range of swing of the loaded arm. Accordingly, the swing of the loaded arm must be reduced by modifying the transmission ratio so as to maintain the resisting force substantially constant over the full range of actuation of the actuatable arm. In general, this can only be achieved with a high transmission ratio which creates problems with respect to the versatility of the device.
To overcome these disadvantages, I have proposed in my German Pat. No. 27 16 281 a more versatile system utilizing a weight which is carried by a cable and connected to the actuating arm via a windlass and an appropriate transmission.
While this arrangement allowed a greater range of training operations and uses, it also did not fully accomplish the desired result of maintaining a more or less constant resistance over the full range of actuating arm displacement where the actuating arm could be swung through 180.degree. or more and through lesser angles with equal effect.
Another disadvantage of earlier training devices and systems has been that these means were not fully able to provide equal and opposite forces for reverse muscular action. In other words, the machine was able to resist a contraction of one set of muscles for an appendage, for example, but was not able to resist the opposite contraction, i.e. the contraction of an opposing set of muscles, accompanied by relaxation of the first set. For example, with flexing of the biceps on one side of the arm, the counteracting muscles relax and a flexing of these muscles with relaxation of the biceps cannot be counteracted on the same training machine without contortions.
In other words, movements of the actuatable member of the machine were more or less uncontrolled in one direction and, in training and conditioning, while a resistance could be provided in one sense, it generally could not be provided in equal manner in the opposite sense so that certain muscles could not be toned and strengthened on certain machines without contortions or complex resetting operations.
Actual back-and-forth movements, consequently, could not be used to strengthen oppositely active sets of muscles.